Research On The Microstructure And Bond Failure Mechanism Of Semi-Flexible Composite Cement/Asphalt Interface

Semi-Flexible Pavement(SFP)is a high-performance cement grout injected into a largeporosity asphalt mixture.It exhibits strong resistance to permeability and rutting,effectively prolonging the service life of the pavement,improving driving comfort and safety,and has broad application and development prospects.Due to the significant differences in material properties,mechanical performance,and deformation between asphalt and cement,the cement/asphalt interface is the weak position of the composite material,and cracks often occur at the cement/asphalt interface and propagate along the interface.Therefore,this paper explores the bonding failure mechanism of the cement/asphalt interface from the microstructure,adhesion,and failure behavior of the cement/asphalt interface.The main work and corresponding research results are as follows:(1)The mechanical properties,deformation capacity,and fracture toughness of SFP were tested by Marshall stability test,splitting tensile test,and SCB semi-circular bending test,and the change of failure mode of composite material fracture surface was studied.The results show that an increase in porosity weakens the contribution of the cement/asphalt interface bonding performance to the mechanical properties of SFP.However,the cement/asphalt interface bonding performance should not be ignored for low porosity or specific loading modes.(2)The temperature factor,the change in cement/asphalt interface bonding strength,cement/asphalt adhesion failure,and asphalt cohesive failure were studied through tensile test and analysis of tensile failure surface.The results show that the temperature-tensile strength curve is consistent with the temperature-complex viscosity curve of asphalt,and the reduction in asphalt cohesive strength is the main factor affecting the weakening of the cement/asphalt interface bonding strength.(3)Scanning electron microscopy and energy spectrum analysis technology,infrared spectroscopy analysis were used to characterize the microstructure,chemical composition,and functional groups of the cement/asphalt interface transition zone.The results show that there is no chemical reaction between cement and asphalt.The oriented distribution of sulfate aluminate cement hydration products on the asphalt side increases the mechanical action force of the cement/asphalt interface and proposes the "cement-asphalt oriented adsorption effect".(4)The interaction ability of cement/asphalt was studied through contact angle test and cement/asphalt slurry rheological test.The reliability of the "cement-asphalt oriented adsorption effect" was verified from the molecular and interfacial angles.